1. Field of the Invention
The present invention generally relates to an optical storage system, in particular, to a spherical aberration (SA) compensation apparatus and method of an optical storage system.
2. Description of Related Art
Generally speaking, in order to achieve better playback and burning quality of optical storage system, it is a critical technique of compensating a spherical aberration (SA) of a light point generated by the optical-pickup-head (OPH) and focused on the disc (e.g. compact disc, digital video disc, blue-ray disc). Currently, the spherical aberration compensation method may be substantially divided into the following three types.
1. The SA is regulated based on the amplitude of focus error (FE) signals.
2. The SA is regulated based on the amplitude of tracking error (TE) signals.
3. A photo sensor is equipped in the OPH, and provides spherical aberration error (SAE) signals to reflect the current state of the SA, and thus the SA is regulated based on the current state.
However, under the condition that the disc is not uniformly dyed, the SA is regulated based on the amplitude of the FE signals (or referred to as the S-curve), which may influence the accuracy in regulating the SA due to the great difference of the reflectivities of different regions of the disc. In addition, when the center of tracks of the disc does not coincide with the physical center of the disc, the eccentricity phenomenon may cause the changes of the included angle between the laser beams emitted by the OPH and the tracks of the disc. Therefore, not only the amplitude of the TE signals is influenced, but also the accuracy in regulating the SA is influenced. Furthermore, if the SAE is used for regulating the SA, a photo sensor must be equipped in the OPH, which may cause the increase of the cost of the OPH.